Electrochromic Device and Method for Manufacturing Electrochromic Device

ABSTRACT

The present invention relates to devices that provide a color change under the influence of an electric voltage, in particular to an electrochromic device and a method for manufacturing such a device. Disclosed is a method for manufacturing an electrochromic device comprising at least two electrodes that are flexible and optically transparent with a hermetically closed space between the electrodes filled with an electrochromic composition, which may contain transparent and insoluble microparticles that function as spacers.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/915,896, filed on Jun. 29, 2020, which is a continuation of U.S.patent application Ser. No. 16/436,731, filed on Jun. 10, 2019, now U.S.Pat. No. 10,698,285 B2, entitled “ELECTROCHROMIC DEVICE AND METHOD FORMANUFACTURING ELECTROCHROMIC DEVICE,” which is a continuation of U.S.patent application Ser. No. 14/300,220, filed Jun. 9, 2014, now U.S.Pat. No. 10,344,208 B2, entitled “ELECTROCHROMIC DEVICE AND METHOD FORMANUFACTURING ELECTROCHROMIC DEVICE.” This application is related toU.S. patent application Ser. No. 14/300,216, filed Jun. 9, 2014, nowU.S. Pat. No. 10,294,415 B2, entitled “ELECTROCHROMIC COMPOSITION ANDELECTROCHROMIC DEVICE USING SAME.” Each of the above recitedapplications is in each case incorporated herein by reference in itsentirety.

BACKGROUND OF THE INVENTION Field of the Invention

The disclosed embodiments relate in general to the field of appliedelectrochemistry, and in particular to methods for manufacturingelectrochromic compositions used in devices with electrically controlledabsorption of light such as light filters of variable optical density,light emission modulators, and information image displays.

Description of the Related Art

Electrochromism is the physical phenomenon found in certain compositionsof reversibly changing predetermined optical properties such as color orlight transmittance with an application of an electrical voltage calleda control voltage. Electrochromism provides the basis for operation ofvarious electrochromic devices, such as smart glass well known topersons of ordinary skill in the art. Various types of optical materialsand structures can be used to construct the aforesaid compounds withelectrochromic properties, with the specific structures being dependenton the specific purpose of the electrochromic device.

Known in the art is a method of manufacturing an electrochromic device(U.S. Pat. No. 4,902,108 issued on Feb. 20, 1990, incorporated herein byreference) wherein an electrically conductive coating of one of twooptically transparent electrodes is coated with a thickened solution ofpolymethylmethacrylate in a low-boiling-point solvent, the solvent thenevaporating to yield a layer of polymethylmethacrylate. Following thisstep, both optically transparent electrodes bond to each other on theperimeter while the electrodes are spaced at a predetermined distancefrom one another, and the thus-formed space is filled through an opening(openings) in the adhesive with an electrochromic solution that containscathodic and anodic components; the filled space is then sealed. Thelayer of polymethylmethacrylate is dissolved, and, as a result, theelectrochromic solution thickens, and this significantly reduces thenegative effect of gravitational “delamination” of the composition inthe electrically colored state. Thus, actually the electrochromiccomposition is prepared only after completing the assembly of theaforementioned electrochromic device, and this limits themanufacturability of the device as a whole. In addition, theelectrochromic composition is a liquid phase having viscosity defined bythe amount of polymeric thickener, and the indifferent electrolytesolution introduced into the electrochromic solution provideselectroconductivity of the latter if the cathodic and anodic componentsare not soluble in the ionic state. An indifferent electrolyte isintroduced into compositions based on quaternary salts of bipyridine.

Also known in the art is a method for manufacturing an electrochromicdevice (U.S. Pat. No. 5,471,337 issued on Nov. 28, 1995, incorporatedherein by reference) wherein the space between the electrodes is filledwith an electrochromic dispersion system comprising the following: adispersion medium in the form of a solvent that is thickened,preferably, with polymethylmethacrylate or is plasticized with a polymersolvent; a dispersion phase in the form of polyoxometalate as thecathodic component; and an anodic component.

Additionally known are methods for making an electrochromic device byobtaining a solid-like film of an electrochromic composition directly inthe device itself by polymerization alone and/or polymerization withcrosslinking of monomer chains with the use of initiators of differenttypes (see EP 0612826 A1 of Aug. 31, 1994; WO 97/34186 of Sep. 18, 1997;and WO 98/42796 of Oct. 1, 1998, incorporated herein by reference).However, such polymerization reactions are accompanied by volumeshrinkage adversely affecting the quality of the electrochromic device.This negative effect can be particularly manifested in electrochromicdevices with large interelectrode spaces (1 to 2 mm) usually provided inelectrochromic devices having large work surfaces (more than 0.5 m²).

Therefore, new and improved methods for manufacturing of electrochromicdevices are needed that would not be subject to the above deficienciesof the prior art technology.

SUMMARY OF THE INVENTION

The inventive methodology is directed to methods and systems thatsubstantially obviate one or more of the above and other problemsassociated with conventional methods for manufacturing electrochromicdevices.

In accordance with one aspect of the embodiments described herein, thereis provided a method for manufacturing an electrochromic devicecomprising at least two flexible electrodes and a hermetically closedspace between the at least two flexible electrodes, at least one of theat least two flexible electrodes being optically transparent, whereinthe hermetically closed space between the at least two flexibleelectrodes is filled with an electrochromic composition, the methodcomprising: preparing an initial deaerated eletrochromic composition inthe form of an electrochromic dispersion system containing at least oneof a suspension and a colloid, wherein a dispersion medium of theelectrochromic dispersion system comprises an electrochromic solutioncomprising a liquid solvent, a cathodic component, an anodic component,a polymerizable low-shrinkage monomer or a monomer mixture, and apolymerization thermal activator, wherein the dispersion phase consistsof a highly dispersible polymer, and wherein the initial electrochromiccomposition is deaerated to remove the dissolved oxygen of air that wereintroduced with the highly dispersible polymer; (2) filling thehermetically closed space between the at least two flexible electrodeswith the deaerated initial electrochromic composition, and (3) sealingthe hermetically closed space between the at least two flexibleelectrodes.

In accordance with another aspect of the embodiments described herein,there is provided an electrochromic device comprising at least twoflexible electrodes and a hermetically closed space between the at leasttwo flexible electrodes, at least one of the at least two flexibleelectrodes being optically transparent, wherein the hermetically closedspace between the at least two flexible electrodes is filled with anelectrochromic composition, the electrochromic device being manufacturedby a method comprising: (1) preparing an initial deaerated eletrochromiccomposition in the form of an electrochromic dispersion systemcontaining at least one of a suspension and a colloid, wherein adispersion medium of the electrochromic dispersion system comprises anelectrochromic solution comprising a liquid solvent, a cathodiccomponent, an anodic component, a polymerizable low-shrinkage monomer ora monomer mixture, and a polymerization thermal activator, wherein thedispersion phase consists of a highly dispersible polymer, and whereinthe initial electrochromic composition is deaerated to remove thedissolved oxygen of air that were introduced with the highly dispersiblepolymer; (2) filling the hermetically closed space between the at leasttwo flexible electrodes with the deaerated initial electrochromiccomposition, and (3) sealing the hermetically closed space between theat least two flexible electrodes.

Additional aspects related to the invention will be set forth in part inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. Aspects ofthe invention may be realized and attained by means of the elements andcombinations of various elements and aspects particularly pointed out inthe following detailed description and the appended claims.

It is to be understood that both the foregoing and the followingdescriptions are exemplary and explanatory only and are not intended tolimit the claimed invention or application thereof in any mannerwhatsoever.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification exemplify the embodiments of the presentinvention and, together with the description, serve to explain andillustrate principles of the inventive technique. Specifically:

FIG. 1 shows the embodiment of an electrochromic device with twooptically transparent electrodes.

FIG. 2 shows the projection of a set of layers that forms theelectrochromic device.

DETAILED DESCRIPTION

In the following detailed description, reference will be made to theaccompanying drawing(s), in which identical functional elements aredesignated with like numerals. The aforementioned accompanying drawingsshow by way of illustration, and not by way of limitation, specificembodiments and implementations consistent with principles of thepresent invention. These implementations are described in sufficientdetail to enable those skilled in the art to practice the invention andit is to be understood that other implementations may be utilized andthat structural changes and/or substitutions of various elements may bemade without departing from the scope and spirit of present invention.The following detailed description is, therefore, not to be construed ina limited sense.

In accordance with one aspect of the embodiments described herein, thereis provided an electrochromic device with an electrochromic compositionin the form of a solid polymer layer that has an increased rate ofdiscoloration in a wide temperature range and that imparts stability tothe electrochromic device operating under conditions that maintain along-term colored state and allow for high-voltage control and change ofelectrode polarity, which result in long-term uniformity of colorationand discoloration, especially for electrochromic devices having largework surface areas.

In accordance with another aspect of the embodiments described herein,there is provided an electrochromic device comprising at least twoelectrodes, wherein the electrodes are flexible and opticallytransparent and the interelectrode space is sealed and filled with theprepared electrochromic composition, as described above. The describeddevice achieves long-term stability of a colored state and may operateunder conditions that allow for high-voltage control and reversal ofelectrode polarity, resulting in uniformity of coloration anddiscoloration. In addition, the described electrochromic device may bemanufactured to have a large surface area.

In one or more embodiments, there is provided a method for manufacturingan electrochromic device comprising at least two electrodes that areflexible and optically transparent with a hermetically closed spacebetween the electrodes filled with an electrochromic composition thatmay contain transparent and insoluble microparticles that function asspacers. In one or more embodiments, the aforesaid method comprises thefollowing steps: preparing an initial electrochromic composition in theform of an electrochromic dispersion system consisting of at least asuspension and/or a colloid, wherein the dispersion medium of saidsystem is an electrochromic solution comprising a liquid solvent, acathodic component, an anodic component, a polymerizable low-shrinkagemonomer, and a polymerization thermal activator. The dispersion phasecomprises a highly dispersible polymer. The initial electrochromiccomposition is deaerated to remove the dissolved oxygen of air that wereintroduced with the highly dispersible polymer and the hermeticallyclosed space between the at least two flexible electrodes is filled withthe initial deaerated electrochromic composition, and the enclosed spacebetween the at least two flexible electrodes is then hermeticallysealed.

In one or more embodiments, the method for manufacturing theelectrochromic device comprises filling the electrochromic device withan electrochromic composition, which, in general, is an electrochromicdispersion system comprising at least a suspension and/or a colloid,wherein the dispersion medium of the system is an electrochromicsolution containing a liquid solvent, a cathodic component, an anodiccomponent, a polymerizable low-shrinkage monomer or monomers, and apolymerization thermal activator. The dispersion phase comprises ahighly dispersible polymer. The initial electrochromic composition isdeaerated to remove the dissolved oxygen of air that were introducedwith the highly dispersible polymer and the hermetically closed spacebetween the at least two flexible electrodes is filled with the initialdeaerated electrochromic composition, and the enclosed space between theat least two flexible electrodes is then hermetically sealed.

In one or more embodiments, the aforesaid electrochromic solution mayadditionally contain an indifferent electrolyte. Provision of anindifferent electrolyte additionally introduced into the dispersionmedium accelerates discoloration of the electrically activatedelectrochromic device and prevents violation of uniformity in colorationand discoloration after operation of the electrochromic device underconditions of long-term polarization with application of DC voltageand/or after application of high voltages.

In one or more embodiments, it is preferable to use the highly dispersedpolymer in an amount sufficient to form a solid layer of theelectrochromic composition, which is characterized by the lack ofvolumetric shrinkage during dissolution of the polymer in theabove-described electrochromic solution over a wide temperature range.

In one or more embodiments, the low-shrinkage monomer is used in anamount sufficient to provide formation of a solid layer, which is formedafter polymerization of the monomer/monomers in the presence of a highdispersible polymer. The monomer/monomers are selected based on theirminimal shrinkage during polymerization. The thermal activator ofpolymerization is used in an amount necessary for the thermal activationof the used monomer or monomers.

In one or more embodiments, the aforesaid liquid solvent is anindividual chemical compound or mixture of chemical compounds.

In one or more embodiments, the cathodic component is an individualorganic electrochromic compound having at polarograms at least onereversible reduction wave or a mixture of such organic electrochromiccompounds. The anodic component is an individual organic electrochromiccompound having at polarograms at least one reversible oxidation wave ora mixture of organic electrochromic compounds.

In one or more embodiments, the composition may further comprisetransparent insoluble microparticles that function as spacers. Thesespacers provide a predetermined distance between the transparent,conductive, flexible electrodes.

In one or more embodiments, deaeration of the initial electrochromiccomposition for removing dissolved oxygen and air introduced with thehighly dispersed polymer can be carried out by evacuation.

In one or more embodiments, the described electrochromic device ismanufactured by using flexible, optically transparent electrodes thatcomprise polymeric substrates (particularly, polyethylene terephthalatesubstrates) coated on one side thereof with a transparent electricallyconductive layer of doped indium oxide (In₂O₃) or doped tin oxide(SnO₂). The electrodes are hermetically bonded around the perimeter sothat the conductive coating is located within the closed space definedbetween the electrodes to prevent contact between the electrodes. Thesealing bond may comprise an adhesive joint that usually contains aspacer or spacers to provide a predetermined distance betweenelectrodes. Since the polymeric substrate with the electrodes depositedon it is flexible and does not provide a gap between the surfaces of theconductive layers, the electrochromic composition may be combined withtransparent insoluble microparticles that function as additionalspacers. These spacers are evenly distributed over the volume occupiedby the electrochromic composition. The spacers are comprised of glass orinsoluble polymeric microparticles of a predetermined size, wherein thematerial of the spacers is selected so that it has a refractive index asclose as possible to the refractive index of the electrochromiccomposition. Dimensions of the spacers can range from 20 μm to 200 μm,and determine the volume to be filled with the electrochromiccomposition.

In one or more embodiments, arranged along the outer perimeter of theadhesive joint or along the longest sides of the electrodes are busbars.The busbars can be located inside the adhesive connection with thewithdrawal of conductors outside. One or several holes are left in theadhesive joint for filling the interelectrode space between the sourceelectrodes with the electrochromic composition. After completion of thefilling operation, the holes are closed with an inert sealant.

In one or more embodiments, to increase the viscosity of theelectrochromic layer and to prevent the phenomenon of gravitationalseparation, the electrochromic composition can be additionally combinedwith a highly dispersible polymer. To further increase viscosity [of thecomposition] after filling the device, the composition can contain someamount of a polymerizable monomer or monomers. Such a monomer (or amonomer mixture) should possess low shrinkage during polymerization.This monomer belongs to the class of monomers polymerizable by acationic mechanism; an example is a cationic ring-openablepolymerization (CROP) monomer. Use of these monomers makes it possiblepractically to avoid shrinkage during the manufacture of theelectrochromic devices. Such an electrochromic layer increasesovervoltage of irreversible electrode reactions that are accompanied bygas evolution, which ensures the stability of the electrochromic deviceagainst the effects of elevated voltages (more than 2 V).

In one or more embodiments, a space between the electrodes is filledwith the initial electrochromic composition through the hole or severalholes left in the adhesive joint.

FIG. 1 shows an embodiment of an electrochromic device with twooptically transparent electrodes. FIG. 2 shows the projection of anexemplary set of layers that forms the embodiment of the electrochromicdevice. The illustrated electrochromic device contains two flexible,optically transparent electrodes 1 and 2, which are deposited onsubstrates 3 and 4, respectively. The substrates 3 and 4 are polymerfilms, the surface areas of which depend on the specific use of theelectrochromic device.

In one or more embodiments, the optically transparent electrodes 1 and 2are provided with busbars 5 and 6, which are arranged over the entireperimeter on surfaces of the electrodes. The substrates 3 and 4 andtheir respective electrodes are bonded together along their perimeter bya sealant 7. Sealing may be done either by adhesive bonding or bythermally fusing the polymer substrates 3 and 4. To ensure apredetermined distance between the conductive, optically transparentelectrodes 1 and 2, the cavity formed between electrodes is filled withspacers 8. The spacers can be made of glass or insoluble polymermicroparticles. The spacers 8 are added to the electrochromiccomposition in the required amount during composition preparation andare uniformly distributed over the volume of the composition during thestage of device filling. After the device is filled with theelectrochromic composition, it is finally sealed. If the polymerizablemonomers contained in the electrochromic composition need thermalactivation, then the device is heated after sealing. By means ofrespective wires 10 and 11, the busbars 5 and 6 are connected to acontrol device 12. When the device is exposed to intensive luminousfluxes, a part of the absorbed energy can be reflected as heat. Toprevent the passage of heat radiation (e.g., into the room), the devicemay be provided with an additional thermally reflective layer 13, whichpromotes reflection of infrared radiation in the outward direction(e.g., to the street).

Example 1

A first exemplary electrochromic device was manufactured to comprise twoflexible, optically transparent SnO₂ electrodes with a surface electricresistance of 35 Ohm/cm² and with a polymeric substrate having athickness of 200 μm. The size of the electrodes was (5×6) cm². Theelectrodes were shifted against one another to provide a current supplyand were glued along the perimeter by means of double-sided adhesivetape having a thickness of 100 μm. A hole was left in the adhesive jointhaving a width of 3 mm for filling the device with the initialelectrochromic composition that comprised a dispersion system in theform of a suspension containing the following components: a dispersionmedium (electrochromic solution), i.e., a solution of 0.01 M1,1′-dibenzyl-4,4′-bipyridinium diperchlorate and 0.01 M1,1′-diethylferrocene in propylene carbonate; and a dispersion phase (33mass %), i.e., a copolymer of polymethylmethacrylate and methacrylicacid. Filling of the internal volume of the device by the initialelectrochromic composition was performed with heating to a temperatureof 70 to 80° C. After completion of the filling operation, the hole inthe adhesive seam was sealed.

In this exemplary electrochromic device, the device transmittance in thevisible range of the spectrum was 75%. Application to the device of 2VDC caused uniform and intense coloring into a blue color in thedirection from the busbars toward the center. At the wavelength of 610nm, the time of shading to the minimal transmittance of 8% was 30 sec.When the voltage reached a steady state and short-circuiting of theelectrodes, the application of voltage was discontinued, and the devicereturned to its initial (transparent) state. The time to completediscoloration was 30 sec.

Example 2

A second exemplary electrochromic device was manufactured as the devicein Example 1, but prior to filling, the initial electrochromiccomposition was evacuated for 15 minutes.

In this exemplary electrochromic device, in the visible range of thespectrum, device transmittance was 78%. Application to the device of 2VDC caused uniform and intense coloring into a blue color. At thewavelength of 610 nm, the time of shading to minimal transmittance of 8%was 25 sec. When the voltage reached a steady state and short-circuitingof the electrodes, the application of voltage was discontinued, and thedevice returned to its initial (transparent) state. The time to completediscoloration was 20 sec.

Example 3

A third exemplary electrochromic device was manufactured as the devicein Example 1, but the initial electrochromic composition contained 3mass % of glass microspheres having a size of 60 μm. The thickness ofthe sealing adhesive layer also was equal to 60 μm.

In this exemplary electrochromic device, the device transmittance in thevisible range of the spectrum was 70%. Application to the device of 2VDC caused uniform and intense coloring into a blue color in thedirection from the busbars toward the center. At the wavelength of 610nm, the time of shading to minimal transmittance of 8% was 30 sec. Whenthe voltage reached a steady state and short-circuiting of theelectrodes, the application of voltage was discontinued, and the devicereturned to its initial (transparent) state. The time to completediscoloration was 30 sec.

In this exemplary electrochromic device, on application of compressivemechanical stress perpendicular to the plane of the device, there was nosignificant change in color uniformity of the device.

Finally, it should be understood that processes and techniques describedherein are not inherently related to any particular apparatus and may beimplemented by any suitable combination of components. Further, varioustypes of general purpose devices may be used in accordance with theteachings described herein. It may also prove advantageous to constructspecialized apparatus to perform the method steps described herein. Thepresent invention has been described in relation to particular examples,which are intended in all respects to be illustrative rather thanrestrictive.

Moreover, other implementations of the invention will be apparent tothose skilled in the art from consideration of the specification andpractice of the invention disclosed herein. Various aspects and/orcomponents of the described embodiments may be used singly or in anycombination in methods for manufacturing electrochromic compositions foruse in devices with electrically controlled absorption of light. It isintended that the specification and examples be considered as exemplaryonly, with a true scope and spirit of the invention being indicated bythe following claims.

What is claimed is:
 1. An electrochromic device comprising: (a) at leasttwo flexible electrodes, wherein at least one of the at least twoflexible electrodes is optically transparent; and (b) a hermeticallyclosed space residing between the at least two flexible electrodes,wherein the hermetically closed space between the at least two flexibleelectrodes is filled with an electrochromic composition, theelectrochromic device being manufactured by a method comprising: (1)preparing an initial deaerated electrochromic composition in the form ofan electrochromic dispersion system containing a colloid, wherein acontinuous phase of the electrochromic dispersion system comprises, anelectrochromic solution comprising a liquid solvent, a cathodiccomponent, an anodic component, a polymerizable low-shrinkage monomer ora monomer mixture comprising a cationic ring-openable polymerizationmonomer, and a polymerization thermal activator, wherein anon-continuous phase, of said electrochromic dispersion system, consistsof a dispersible polymer, wherein said non-continuous phase is saidcolloid, and wherein the initial electrochromic composition is deaeratedto remove the dissolved oxygen of air that was introduced with thedispersible polymer; (2) filling the hermetically closed space betweenthe at least two flexible electrodes with the deaerated initialelectrochromic composition; and (3) sealing the hermetically closedspace between the at least two flexible electrodes.
 2. Theelectrochromic device of claim 1, wherein the continuous phase of theelectrochromic dispersion system further comprises an indifferentelectrolyte.
 3. The electrochromic device of claim 1 wherein, saidliquid solvent comprises propylene carbonate, said cathodic componentcomprises 1,1′-dibenzyl-4,4′-bipyridinium diperchlorate, and said anodiccomponent comprises 1,1′-diethylferrocene.
 4. The electrochromic deviceof claim 1, further comprising a plurality of transparent spacerspositioned within said hermitically closed space, wherein saidtransparent spacers are insoluble in said electrochromic composition,and provide a predetermined distance between the at least two flexibleelectrodes.
 5. The electrochromic device of claim 4, wherein saidtransparent spacers have a refractive index that is close to therefractive index of said electrochromic composition.
 6. Theelectrochromic device of claim 5, wherein said transparent spacerscomprise at least one of glass microparticles or polymericmicroparticles, and each transparent spacer independently has dimensionsof from 20 μm to 200 μm.
 7. The electrochromic device of claim 1,wherein each flexible electrode independently comprises a polymericsubstrate and a transparent electrically conductive layer on a surfaceof said polymeric substrate, wherein said transparent electricallyconductive layer faces said hermitically sealed space.
 8. Theelectrochromic device of claim 7, wherein each transparent electricallyconductive layer independently comprises at least one of doped indiumoxide (In₂O₃) or doped tin oxide (SnO₂).
 9. The electrochromic device ofclaim 7, wherein each polymeric substrate independently comprisespolyethylene terephthalate.